The database keeps almost the whole Dojo.1.6 libraries inside. And at load time there are several checks were to get the correct Dojo files.
And in 8.5.3 the loading of the several dojo files will be smarter. It will only load the files that are necessary. That will in decrease loadtime. 8.5.3 will have Dojo 1.5, which contains the dojox.mobile component.